Cyclobutane derivatives

ABSTRACT

The invention relates to novel cyclobutane derivatives of the formula (I), in which R 1 , R 2 , A, Z, m, n and o have the meaning indicated in claim 1, to the use thereof as components of liquid-crystalline media, and to liquid-crystal and electro-optical display elements which contain the liquid-crystalline media according to the invention.

The present invention relates to cyclobutane derivatives which containboth a CF₂O bridge as constituent of their mesogenic skeleton and abutane-1,4-diyl group as part of a spiroalkane unit, to the use thereofas component(s) of liquid-crystalline media, and to liquid-crystal andelectro-optical display elements which contain these liquid-crystallinemedia according to the invention.

The cyclobutane derivatives according to the invention can be used ascomponents of liquid-crystalline media, in particular for displays basedon the principle of the twisted cell, the guest-host effect, the effectof deformation of aligned phases DAP or ECB (electrically controlledbirefringence), the IPS effect (in-plane switching) or the effect ofdynamic scattering.

All the substances employed hitherto for this purpose have certaindisadvantages, for example inadequate stability to the effect of heat,light or electric fields, or unfavourable elastic and/or dielectricproperties.

The invention thus had the object of finding novel stableliquid-crystalline or mesogenic compounds which are suitable ascomponents of liquid-crystalline media, in particular for TN, STN, IPSand TFT displays.

A further object of the present invention was to provideliquid-crystalline compounds which have low rotational viscosity, resultin an improvement in low-temperature stability in liquid-crystalmixtures, and can be synthesised simply. In particular through thereduction in the rotational viscosity, it should be possible to achievesignificantly shorter response times.

Surprisingly, it has been found that the cyclobutane derivativesaccording to the invention are eminently suitable as components ofliquid-crystalline media. They can be used to obtain stableliquid-crystalline media, particularly suitable for TFT or STN displays.

The physical properties of the cyclobutane derivatives according to theinvention can be varied in broad ranges through a suitable choice of thering members and/or the terminal substituents. Thus, for example, it ispossible to obtain cyclobutane derivatives according to the inventionhaving very low optical anisotropy values or low positive to highly positive dielectric anisotropy values.

In particular, the cyclobutane derivatives according to the inventionare distinguished by high clearing points at the same time asunexpectedly low rotational viscosity.

Liquid-crystalline media having very low optical anisotropy values areof particular importance for reflective and transflective applications,i.e. applications in which the respective LCD experiences no or onlysupporting backlighting.

The provision of the cyclobutane derivatives according to the inventionvery generally considerably broadens the range of liquid-crystallinesubstances which are suitable, from various applicational points ofview, for the preparation of liquid-crystalline mixtures.

The cyclobutane derivatives according to the invention have a broadrange of applications. Depending on the choice of the substituents,these compounds can serve as base materials of which liquid-crystallinemedia are predominantly composed; however, it is also possible to addliquid-crystalline base materials from other classes of compound to thecyclo-butane derivatives according to the invention in order, forexample, to influence the dielectric and/or optical anisotropy of adielectric of this type and/or to optimise its threshold voltage and/orits viscosity.

In the pure state, the cyclobutane derivatives according to theinvention are colourless and form liquid-crystalline mesophases in atemperature range which is favourably located for electro-optical use.They are stable chemically, thermally and to light.

The present invention thus relates to cyclobutane derivatives of theformula I

in which

-   R¹, R² are identical or different and each, independently of one    another, denote H, halogen (F, Cl, Br or I) or a linear or branched,    optionally chiral alkyl or alkoxy radical having 1 to 15 C atoms    which is unsubstituted or mono- or polysubstituted by halogen and in    which one or more CH₂ groups may each be replaced, independently of    one another, by —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CH═CH—,    —CH═CF—, —CF═CF—, —C≡C— or    in such a way that heteroatoms are not linked directly to one    another, —CN, —SCN, —NCS, —SF₅, —SCF₃, —CF₃, —CF═CF₂, —CF₂CF₂CF₃,    —OCF₃, —OCHF₂, —CF₂CH₂CF₃ or —OCH₂CF₂CHFCF₃,-   A is identical or different and in each case, independently of one    another, denotes    -   a) trans-1,4-cyclohexylene, in which, in addition, one or more        non-adjacent CH₂ groups may be replaced by —O— and/or —S— and in        which, in addition, one or more H atoms may be replaced by F,    -   b) 1,4-phenylene, in which one or two CH groups may be replaced        by N and in which, in addition, one or more H atoms may be        replaced by halogen (F, Cl, Br or I), —CN, —CH₃, —CHF₂, —CH₂F,        —OCH₃, —OCHF₂ or —OCF₃,    -   c) a radical from the group bicyclo[1.1.1]pentane-1,3-diyl,        bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl,        naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl,        1,2,3,4-tetrahydronaphthalene-2,6-diyl and piperidine-1,4-diyl,        or    -   d) 1,4-cyclohexenylene,-   Z is identical or different and in each case, independently of one    another, denotes —O—, —CH₂O—, —OCH₂—, —CO—O—, —O—CO—, —CF₂O—,    —OCF₂—, —CF₂CF₂—, —CH₂CF₂—, —CF₂CH₂—, —CH₂CH₂—, —CH═CH—, —CH═CF—,    —CF═CH—, —CF═CF—, —CF═CF—COO—, —O—CO—CF═CF—, —C≡C— or a single bond,-   m, n are identical or different and, independently of one another,    denote 0, 1 or 2, preferably m=0 or 1 and n=1 or 2, and-   o denotes 0 or 1.

The present invention furthermore relates to the use of compounds of theformula I as component(s) of liquid-crystalline media.

The present invention likewise relates to liquid-crystalline mediahaving at least two liquid-crystalline components which comprise atleast one compound of the formula 1.

The present invention also relates to liquid-crystal display elements,in particular electro-optical display elements, which contain, asdielectric, a liquid-crystalline medium according to the invention.

Particular preference is given to reflective and transflectiveliquid-crystal display elements and other liquid-crystal displays of lowbirefringence Δn, so-called “low Δn mode displays”, such as, forexample, reflective and transflective TN displays.

The meaning of the formula I includes all isotopes of the chemicalelements bound in the compounds of the formula I. In enantiomericallypure or enriched form, the compounds of the formula I are also suitableas chiral dopants and in general for achieving chiral mesophases.

Above and below, R¹, R², A, Z, m, n and o have the meaning indicated,unless expressly stated otherwise. If the radicals A and Z occur morethan once, they may, independently of one another, adopt identical ordifferent meanings.

Preference is given to compounds of the formula I in which R¹ is H or alinear alkyl radical having 1 to 10 C atoms.

Preference is likewise given to compounds of the formula I in which R²denotes H, a linear alkoxy radical having 1 to 10 C atoms, —F, —Cl,—CF₃, —OCF₃, —OCHF₂, —CN, —NCS or —SF₅, particularly preferably —OC₂H₅,—F, —CF₃, —OCF₃ or —CN.

Preferred compounds of the formula I are compounds of the sub-formula Ia

and compounds of the sub-formula Ib

in which R¹, R², A, Z, m and n have the meanings indicated above.

Z preferably denotes —CH₂CH₂—, —CH═CH—, —C≡C—, —CF₂CF₂—, —CF═CF—, —CF₂O—or a single bond, particularly preferably a single bond.

For reasons of simplicity, Cyc below denotes a 1,4-cyclohexyleneradical, Che denotes a 1,4-cyclohexenylene radical, Dio denotes a1,3-dioxane-2,5-diyl radical, Dit denotes a 1,3-dithiane-2,5-diylradical, Phe denotes a 1,4-phenylene radical, Pyd denotes apyridine-2,5-diyl radical, Pyr denotes a pyrimidine-2,5-diyl radical,Bco denotes a bicyclo[2.2.2]octylene radical and Dec denotes adecahydronaphthalene-2,6-diyl radical, where Cyc and/or Phe may beunsubstituted or mono- or polysubstituted by CH₃, Cl, F or CN.

A preferably denotes Phe, Cyc, Che, Pyd, Pyr or Dio, and particularlypreferably Phe or Cyc.

Phe preferably denotes

The terms 1,3-dioxane-2,5-diyl and Dio each encompass the two positionalisomers

The cyclohexene-1,4-diyl group preferably has the following structures:

Particularly preferred compounds of the formula Ia include the followingformulae:

Particularly preferred compounds of the formula Ib include the followingformulae:

in which R¹, R², A and Z have the meanings indicated above, and L¹, L²,L³, L⁴, L⁵ and L⁶, are identical or different and, independently of oneanother, denote H or F.

Preference is given to compounds of the formulae Iaa to lap and Iba toIbp in which R¹ denotes H or a linear alkyl or alkoxy radical having 1to 10 C atoms or alkenyl or alkenyloxy having 2 to 10 C atoms.

Preference is likewise given to compounds of the formulae Iaa to lap andIba to Ibp in which R² denotes —F, —CF₃, —OCF₃, —CN, —NCS, —SF₅ or—OC₂H₅.

Particular preference is given to compounds of the formulae Iaa to Iahand Iba to Ibh in which R² denotes —F, —CF₃, —OCF₃, —CN, —NCS or —SF₅,L¹ and L², are identical or different and, independently of one another,denote F or H, and L³ and L⁴ denote H.

Particular preference is given to compounds of the formulae Iaa to Iahand Iba to Ibh in which R² is —OC₂H₅, L² and L³, are identical ordifferent and are, independently of one another, F or H, and L¹ and L⁴are H.

Particular preference is given to compounds of the formulae Iai to Iapand Ibi to Ibp in which R² denotes —F, —CF₃, —OCF₃, —CN, —NCS or —SF₅,L¹, L², L⁵ and L⁶, are identical or different and, independently of oneanother, denote F or H, and L³ and L⁴ denote H.

Particular preference is given to compounds of the formulae Iai to Iapand Ibi to Ibp in which R² denotes —OC₂H₅, L², L³ and L⁶, are identicalor different and, independently of one another, denote F or H, and L¹,L⁴ and L⁵ denote H.

In the compounds of the formulae Iab, Iaj, Ibb and Ibj, Z preferablydenotes —CH₂CH₂—, —CF₂CF₂—, —CF₂O— or a single bond, particularlypreferably a single bond.

In the compounds of the formulae Iag, Iao, Ibg and Ibo, A is preferably

If R¹ and/or R² in the formulae above and below denote an alkyl radical,this may be straight-chain or branched. It is particularly preferablystraight-chain, has 2, 3, 4, 5, 6 or 7 C atoms and accordingly denotesethyl, propyl, butyl, pentyl, hexyl or heptyl, furthermore methyl,octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl orpentadecyl.

If R¹ and/or R² denotes an alkyl radical in which one CH₂ group has beenreplaced by —O—, this may be straight-chain or branched. It ispreferably straight-chain and has 1 to 10 C atoms. The first CH₂ groupof this alkyl radical has particularly preferably been replaced by —O—,so that the radical R¹ and/or R² attains the meaning alkoxy and, inparticular, denotes methoxy, ethoxy, propoxy, butoxy, pentyloxy,hexyloxy, heptyloxy, octyloxy or nonyloxy.

Furthermore, a CH₂ group elsewhere may also be replaced by —O—, so thatthe radical R¹ and/or R² preferably denotes straight-chain 2-oxapropyl(=methoxymethyl), 2-(=ethoxymethyl) or 3-oxabutyl (=2-methoxyethyl), 2-,3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or8-oxanonyl, or 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl.

If R¹ and/or R² denotes an alkyl radical in which one CH₂ group has beenreplaced by —CH═CH—, this may be straight-chain or branched. It ispreferably straight-chain and has 2 to 10 C atoms. Accordingly, itdenotes vinyl, prop-1- or -2-enyl, but-1-, -2- or -3-enyl, pent-1-, -2-,-3- or 4-enyl, hex-1-, -2-, -3-, -4- or -5-enyl, hept-1-, -2-, -3-, 4-,-5- or -6-enyl, oct-1-, -2-, -3-, 4-, -5-, -6- or -7-enyl, non-1-, -2-,-3-, -4-, -5-, -6-, -7- or -8-enyl, or dec-1-, -2-, -3-, 4-, -5-, -6-,-7-, -8- or -9-enyl.

Preferred alkenyl groups are C₂-C₇₁ E-alkenyl, C₄-C₇-3E-alkenyl,C₅-C₇-4-alkenyl, C₆-C₇-5-alkenyl and C₇-6-alkenyl, particularlypreferably C₂-C₇-1E-alkenyl, C₄-C₇-3E-alkenyl and C₅-C₇-4-alkenyl.

Examples of particularly preferred alkenyl groups are vinyl,1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl,3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl,4E-hexenyl, 4Z-heptenyl, 5-hexenyl and 6-heptenyl. Groups having up to 5carbon atoms are particularly preferred.

If R¹ and/or R² denotes an alkyl radical in which one CH₂ group has beenreplaced by —O— and one has been replaced by —CO—, these are preferablyadjacent. These thus contain an acyloxy group —CO—O— or an oxycarbonylgroup —O—CO—. These are particularly preferably straight-chain and have2 to 6 C atoms.

Accordingly, they denote in particular acetoxy, propionyloxy,butyryloxy, pentanoyloxy, hexanoyloxy, acetoxymethyl,propionyloxymethyl, butyryS oxymethyl, pentanoyloxymethyl,2-acetoxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 3-acetoxypropyl,3-propionyloxypropyl, 4-acetoxybutyl, methoxycarbonyl, ethoxycarbonyl,propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl,ethoxycarbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl,2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl,2-(propoxycarbonyl)ethyl, 3-(methoxycarbonyl)propyl,3-(ethoxycarbonyl)propyl or 4-(methoxycarbonyl)butyl.

If R¹ and/or R² denotes an alkyl radical in which one CH₂ group has beenreplaced by unsubstituted or substituted —CH═CH— and an adjacent CH₂group has been replaced by CO, CO—O or O—CO, this may be straight-chainor branched. It is preferably straight-chain and has 4 to 13 C atoms.Accordingly, it particularly preferably denotes acryloyloxymethyl,2-acryloyloxyethyl, 3-acryloyloxypropyl, 4-acryloyloxybutyl,5-acryloyloxypentyl, 6-acryloyloxyhexyl, 7-acryloyloxyheptyl,8-acryloyloxyoctyl, 9-acryloyloxynonyl, 10-acryloyloxydecyl,methacryloyloxymethyl, 2-methacryloyloxyethyl, 3-methacryloyloxypropyl,4-methacryloyloxybutyl, 5-methacryloyloxypentyl, 6-methacryloyloxyhexyl,7-methacryloyloxyheptyl, 8-methacryloyloxyoctyl or9-methacryloyloxynonyl.

If R¹ and/or R² denotes an alkyl or alkenyl radical which ismonosubstituted by CN or CF₃, this radical is preferably straight-chainand substitution by CN or CF₃ is in the co-position.

If R¹ and/or R² denotes an alkyl radical which is at leastmonosubstituted by halogen, this radical is preferably straight-chain.Halogen is preferably F or Cl. In the case of polysubstitution, halogenis preferably F. The resultant radicals also include perfluorinatedradicals. In the case of monosubstitution, the fluorine or chlorinesubstituent can be in any desired position, but is preferably in theco-position.

Compounds of the formula I having a branched wing group R¹ and/or R² mayoccasionally be of importance owing to better solubility in theconventional liquid-crystalline base materials, but in particular aschiral dopants if they are optically active. Smectic compounds of thistype are suitable as components of ferroelectric materials.

Branched groups of this type generally contain not more than one chainbranch. Preferred branched radicals R¹ and/or R² are isopropyl, 2-butyl(=1-methylpropyl), isobutyl (=2-methylpropyl), 2-methylbutyl, isopentyl(=3-methylbutyl), 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl,2-propylpentyl, isopropoxy, 2-methylpropoxy, 2-methylbutoxy,3-methylbutoxy, 2-methylpentyloxy, 3-methylpentyloxy, 2-ethylhexyloxy,1-methylhexyloxy and 1-methylheptyloxy.

The formula I encompasses both the racemates of these compounds and theoptical antipodes, and mixtures thereof.

Of the compounds of the formula I and the sub-formulae, preference isgiven to those in which at least one of the radicals present therein hasone of the preferred meanings indicated.

The compounds of the formula I are prepared by methods known per se, asdescribed in the literature (for example in the standard works, such asHouben-Weyl, Methoden der Organischen Chemie [Methods of OrganicChemistry], Georg-Thieme-Verlag, Stuttgart), to be precise underreaction conditions which are known and suitable for the said reactions.Use can be made here of variants which are known per se, but are notmentioned here in greater detail.

The compounds of the formula I can be prepared, for example, inaccordance with the following reaction schemes or analogously thereto.Further synthetic methods are given in the examples.

In schemes 1 to 4, R¹, R², A, Z, n, m and o have the meanings indicatedabove. L¹, L², L³, L⁴, L⁵ and L⁶, are identical or different and,independently of one another, denote H or F.

The starting materials are either known or can be prepared analogouslyto known compounds.

If desired, the starting materials can also be formed in situ by notisolating them from the reaction mixture, but instead immediatelyconverting them further into the compounds of the formula I.

The liquid-crystalline media according to the invention preferablycomprise 2 to 40, particularly preferably 4 to 30, components as furtherconstituents besides one or more compounds according to the invention.In particular, these media comprise 7 to 25 components besides one ormore compounds according to the invention. These further constituentsare preferably selected from nematic or nematogenic (monotropic orisotropic) substances, in particular substances from the classes of theazoxybenzenes, benzylideneanilines, biphenyls, terphenyls, phenyl orcyclohexyl benzoates, phenyl or cyclohexyl esters ofcyclohexanecarboxylic acid, phenyl or cyclohexyl esters ofcyclohexylbenzoic acid, phenyl or cyclohexyl esters ofcyclohexylcyclohexanecarboxylic acid, cyclohexylphenyl esters of benzoicacid, of cyclohexanecarboxylic acid or ofcyclohexylcyclohexanecarboxylic acid, phenylcyclohexanes,cyclohexylbiphenyls, phenylcyclohexylcyclohexanes,cyclohexylcyclohexanes, cyclohexylcyclohexylcyclohexenes,1,4-biscyclohexylbenzenes, 4,4′-biscyclohexylbiphenyls, phenyl- orcyclohexylpyrimidines, phenyl- or cyclohexylpyridines, phenyl- orcyclohexyldioxanes, phenyl- or cyclohexyl-1,3-dithianes,1,2-diphenylethanes, 1,2-dicyclohexylethanes,1-phenyl-2-cyclohexylethanes,1-cyclohexyl-2-(4-phenylcyclohexyl)ethanes,1-cyclohexyl-2-biphenylylethanes, 1-phenyl-2-cyclohexylphenylethanes,optionally halogenated stilbenes, benzyl phenyl ethers, tolans andsubstituted cinnamic acids. The 1,4-phenylene groups in these compoundsmay also be fluorinated.

The most important compounds suitable as further constituents of themedia according to the invention can be characterised by the formulae 1,2, 3, 4 and 5:R′-L-E-R″  1R′-L-COO-E-R″  2R′-L-OOC-E-R″  3R′-L-CH₂CH₂-E-R″  4R′-L-C≡C-E-R″  5

In the formulae 1, 2, 3, 4 and 5, L and E, which may be identical ordifferent, each, independently of one another, denote a divalent radicalfrom the group formed by -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-,-Pyr-, -Dio-, -G-Phe- and -G-Cyc- and their mirror images, where Phedenotes unsubstituted or fluorine-substituted 1,4-phenylene, Cyc denotestrans-1,4-cyclohexylene or 1,4-cyclohexenylene, Pyr denotespyrimidine-2,5-diyl or pyridine-2,5-diyl, Dio denotes1,3-dioxane-2,5-diyl and G denotes 2-(trans-1,4-cyclohexyl)ethyl.

One of the radicals L and E preferably denotes Cyc, Phe or Pyr. Epreferably denotes Cyc, Phe or Phe-Cyc. The media according to theinvention preferably comprise one or more components selected from thecompounds of the formulae 1, 2, 3, 4 and 5 in which L and E are selectedfrom the group Cyc, Phe and Pyr and simultaneously one or morecomponents selected from the compounds of the formulae 1, 2, 3, 4 and 5in which one of the radicals L and E is selected from the group Cyc, Pheand Pyr and the other radical is selected from the group -Phe-Phe-,-Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-, and optionally one or morecomponents selected from the compounds of the formulae 1, 2, 3, 4 and 5in which the radicals L and E are selected from the group -Phe-Cyc-,-Cyc-Cyc-, -G-Phe- and -G-Cyc-.

R′ and/or R″ each, independently of one another, denote alkyl, alkenyl,alkoxy, alkoxyalkyl, alkenyloxy or alkanoyloxy having up to 8 C atoms,—F, —Cl, —CN, —NCS, —(O)_(i)CH_(3-(k+l))F_(k)Cl_(l), where i denotes 0or 1, k and l, are identical or different and, independently of oneanother, denote 0, 1, 2 or 3, and the following applies to the sum(k+l): 1≦(k+l)≦3.

In a smaller sub-group of the compounds of the formulae 1, 2, 3, 4 and5, R′ and R″ each, independently of one another, denote alkyl, alkenyl,alkoxy, alkoxyalkyl, alkenyloxy or alkanoyloxy having up to 8 C atoms.This smaller sub-group is called group A below, and the compounds arereferred to by the sub-formulae 1a, 2a, 3a, 4a and 5a. In most of thesecompounds, R′ and R″ are different from one another, one of theseradicals usually being alkyl, alkenyl, alkoxy or alkoxyalkyl.

In another smaller sub-group of the compounds of the formulae 1, 2, 3, 4and 5, which is known as group B, R″ is —F, —Cl, —NCS or—(O)_(i)CH_(3(k+l))F_(k)C_(l), where i denotes 0 or 1, k and l, areidentical or different and, independently of one another, denote 1, 2 or3, and the following applies to the sum (k+l): 1≦(k+l)≦3. The compoundsin which R″ has this meaning are referred to by the sub-formulae 1b, 2b,3b, 4b and 5b. Particular preference is given to those compounds of thesub-formulae 1b, 2b, 3b, 4b and 5b in which R″ denotes —F, —Cl, —NCS,—CF₃, —OCHF₂ or —OCF₃.

In the compounds of the sub-formulae 1b, 2b, 3b, 4b and 5b, R′ has themeaning indicated for the compounds of the sub-formulae 1a to 5a and ispreferably alkyl, alkenyl, alkoxy or alkoxyalkyl.

In a further smaller sub-group of the compounds of the formulae 1, 2, 3,4 and 5, R″ denotes —CN. This sub-group is referred to below as group C,and the compounds of this sub-group are correspondingly described bysub-formulae 1c, 2c, 3c, 4c and 5c. In the compounds of the sub-formulae1c, 2c, 3c, 4c and 5c, R′ has the meaning indicated for the compounds ofthe sub-formulae 1a to 5a and preferably denotes alkyl, alkoxy oralkenyl.

Besides the preferred compounds of groups A, B and C, other compounds ofthe formulae 1, 2, 3, 4 and 5 having other variants of the proposedsubstituents are also customary. All these substances are obtainable bymethods which are known from the literature or analogously thereto.

Besides the compounds of the formula I according to the invention, themedia according to the invention preferably comprise one or morecompounds selected from groups A, B and/or C. The proportions by weightof the compounds from these groups in the media according to theinvention are preferably

-   group A: 0 to 90%, preferably 20 to 90%, in particular 30 to 90%-   group B: 0 to 80%, preferably 10 to 80%, in particular 10 to 65%-   group C: 0 to 80%, preferably 5 to 80%, in particular 5 to 50%,    where the sum of the proportions by weight of the group A, B and/or    C compounds present in the respective media according to the    invention is preferably 5 to 90% and in particular 10 to 90%.

The media according to the invention preferably comprise 1 to 40%,particularly preferably 5 to 30%, of the compounds of the formula Iaccording to the invention. Preference is furthermore given to mediacomprising more than 40%, particularly preferably 45 to 90%, ofcompounds of the formula I according to the invention. The mediapreferably comprise three, four or five compounds according to theinvention.

The liquid-crystal mixtures which can be used in accordance with theinvention are prepared in a manner which is conventional per se. Ingeneral, the desired amount of the components used in lesser amount isdissolved in the components making up the principal constituent,preferably at elevated temperature. It is also possible to mix solutionsof the components in an organic solvent, for example in acetone,chloroform or methanol, and to remove the solvent again, for example bydistillation, after thorough mixing. It is furthermore possible toprepare the mixtures in other conventional manners, for example by usingpremixes, for example homologue mixtures, or using so-called“multibottle” systems.

The dielectrics may also comprise further additives known to the personskilled in the art and described in the literature. For example, 0 to15%, preferably 0 to 10%, of pleochroic dyes and/or chiral dopants canbe added. The individual compounds added are employed in concentrationsof 0.01 to 6%, preferably 0.1 to 3%. However, the concentration data ofthe other constituents of the liquid-crystal mixtures, i.e. theliquid-crystalline or mesogenic compounds are indicated without takinginto account the concentration of these additives.

In the present application and in the following examples, the structuresof the liquid-crystal compounds are indicated by means of acronyms, thetransformation into chemical formulae taking place in accordance withTables A and B below. All radicals C_(n)H_(2n+1) and C_(m)H_(2m+1) arestraight-chain alkyl radicals having n and m C atoms respectively n andm are an integers, preferably 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12,where n=m or n≠m. The coding in Table B is self-evident. In Table A,only the acronym for the parent structure is indicated. In individualcases, the acronym for the parent structure is followed, separated by adash, by a code for the substituents R¹*, R²*, L¹* and L²*: Code forR¹*, R²*, L¹*, L²* R¹* R²* L¹* L²* nm C_(n)H_(2n+1) C_(m)H_(2m+1) H HnOm C_(n)H_(2n+1) OC_(m)H_(2m+1) H H nO.m OC_(n)H_(2n+1) C_(m)H_(2m+1) HH nN C_(n)H_(2n+1) CN H H nN.F C_(n)H_(2n+1) CN H F nN.F.F C_(n)H_(2n+1)CN F F nF C_(n)H_(2n+1) F H H nOF OC_(n)H_(2n+1) F H H nF.FC_(n)H_(2n+1) F H F nmF C_(n)H_(2n+1) C_(m)H_(2m+1) H F nCF₃C_(n)H_(2n+1) CF₃ H H nOCF₃ C_(n)H_(2n+1) OCF₃ H H n-Vm C_(n)H_(2n+1)—CH═CH—C_(m) H H H_(2m+1) nV-Vm C_(n)H_(2n+1)—CH═CH— —CH═CH—C_(m) H HH_(2m+1)

Preferred mixture components are indicated in Tables A and B. TABLE A

TABLE B

TABLE C Table C shows possible dopants which are preferably added to themix- tures according to the invention.

Particular preference is given to mixtures according to the inventionwhich, besides one or more compounds of the formula I, comprise two,three or more compounds selected from Table B.

The following examples are intended to explain the invention withoutlimiting it. Above and below, percentages are percent by weight. Alltemperatures are given in degrees Celsius. m.p. denotes melting pointand cl.p.=clearing point. Furthermore, C=crystalline state, N=nematicphase, Sm=smectic phase and I=isotropic phase. The data between thesesymbols represent the transition temperatures. Δn denotes opticalanisotropy (589 nm, 20° C.), and Δε the dielectric anisotropy (1 kHz,20° C.).

The Δn and Δε values of the compounds according to the invention wereobtained by extrapolation from liquid-crystalline mixtures whichconsisted of 10% of the respective compound according to the inventionand 90% of the commercially available liquid crystal ZLI 4792 (Merck,Darmstadt).

“Conventional work-up” means that water is added if necessary, themixture is extracted with methylene chloride, diethyl ether or toluene,the phases are separated, the organic phase is dried and evaporated, andthe product is purified by distillation under reduced pressure orcrystallisation and/or chromatography.

Above and below, the following abbreviations are used:

-   DBH 1,3-dibromo-5,5-dimethylhydantoin-   DMF dimethylformamide-   LDA Lithium diisopropylamide-   n-BuLi n-butyllithium-   RT room temperature (about 20° C.)-   THF tetrahydrofuran

EXAMPLE 1

The compound of the following formula

2-(difluoro[3,4,5-trifluorophenyl]oxymethyl)-6-(4-propylcyclohexyl)spiro-[3.3]heptane[7]

is prepared as follows:

Reagents and reaction conditions: a) trichloroacetyl chloride, Zn,ether; b) Zn, HOAc; c) (Ph₃P)CH⁺Br⁻, KOtBu, THF;2-trimethylsilyl-1,3-dithiane, nBuLi, THF, −78° C.→RT; e) 1.3,4,5-trifluorophenol, Et₃N, CH₂Cl₂, −78° C.; 2. Et₃N.3HF, DBH, 78°C.→RT.

Step 1

2-(6-{4-n-Propylcyclohexyl}spiro[3.3]hept-2-ylidene)[1,3]dithiane 6

15.5 g (80.3 mmol) of 2-trimethylsilyl-1,3-dithiane are dissolved in 150ml of THF, and 51 ml (80.3 mmol) of n-BuLi (15 percent in hexane) arerapidly added dropwise at −70° C. The batch is subsequently allowed tothaw to 0° C. over the course of 4 hours, stirred for 10 minutes withoutcooling and re-cooled to −70° C., and a solution of 17.0 g (72.5 mmol)of 6-(4-n-propylcyclohexyl)spiro[3.3]heptan-2-one 5 in 50 ml of THF isadded drop-wise. The batch is left to stir overnight at roomtemperature, hydrolysed using saturated sodium hydrogencarbonatesolution and extracted with dichloromethane. The combined organic phasesare washed with water and dried over sodium sulfate. The solvent isremoved under reduced pressure, and the crude product is recrystallisedfrom n-heptane. The dithioacetal 6 is obtained as colourless flakes.

Step 2

10.0 g (29.7 mmol) of the dithioacetal 6 are dissolved in 100 ml ofdichloro-methane, and 2.6 ml (30.0 mmol) of trifluoromethanesulfonicacid are added dropwise with ice/common salt cooling. After 5 minutes,the cooling is removed, and the batch is stirred at room temperature for45 minutes. The batch is subsequently cooled to −70° C., a mixture of7.5 ml (54.0 mmol) of triethylamine and 6.67 g (45.0 mmol) oftrifluorophenol in 30 ml of dichloromethane is added, and the mixture isstirred at −70° C. for 1 hour. 24.2 ml (0.150 mol) of triethylaminetris(hydrofluoride) are then added, and, after 5 minutes, 42.9 g (0.150mol) of DBH, suspended in 60 ml of dichloromethane, are added inportions over the course of about 30 minutes. After 90 minutes, thebatch is allowed to thaw and is hydro-lysed using 1 M sodium hydroxidesolution and aqueous hydrogen sulfite solution. The organic phase isseparated off, washed with saturated sodium chloride solution and driedover sodium sulfate. The solvent is removed under reduced pressure, andthe residue is filtered through silica gel with n-heptane, giving thespiro compound 7 as a colourless solid of melting point: 43° C.

C 43 N 46.6 I

Δε=9.1

Δn=0.0668

γ₁=132 mPa·s

¹⁹F-NMR (235 MHz, CDCl₃)

δ=−79.2 ppm (d, ³J_(F,H)=10.6 Hz, 2 F, CF₂O), −133.2 (m_(c), 2 F, Ar—F),−164.7 (tt, ³J_(F,F)=20.8 Hz, ⁴J_(F,H)=5.9 Hz, 1 F, Ar—F).

The following compounds according to the invention are obtainedanalogously to Example 1 using the corresponding precursors:

Examples R¹ L¹ L² L³ L⁴ R² 1. 127. 253. 379. C₃H₇ F F H H F 2. 128. 254.380. C₃H₇ F H H H F 3. 129. 255. 381. C₃H₇ H H H H F 4. 130. 256. 382.C₂H₅ H H H H F 5. 131. 257. 383. C₂H₅ F H H H F 6. 132. 258. 384. C₂H₅ FF H H F 7. 133. 259. 385. C₄H₉ H H H H F 8. 134. 260. 386. C₄H₉ F H H HF 9. 135. 261. 387. C₄H₉ F F H H F 10. 136. 262. 388. C₅H₁₁ H H H H F11. 137. 263. 389. C₅H₁₁ F H H H F 12. 138. 264. 390. C₅H₁₁ F F H H F13. 139. 265. 391. C₆H₁₃ H H H H F 14. 140. 266. 392. C₆H₁₃ F H H H F15. 141. 267. 393. C₆H₁₃ F F H H F 16. 142. 268. 394. C₇H₁₅ H H H H F17. 143. 269. 395. C₇H₁₅ F H H H F 18. 144. 270. 396. C₇H₁₅ F F H H F19. 145. 271. 397. C₂H₅ H H H H CF₃ 20. 146. 272. 398. C₂H₅ F H H H CF₃21. 147. 273. 399. C₂H₅ F F H H CF₃ 22. 148. 274. 400. C₃H₇ H H H H CF₃23. 149. 275. 401. C₃H₇ F H H H CF₃ 24. 150. 276. 402. C₃H₇ F F H H CF₃25. 151. 277. 403. C₄H₉ H H H H CF₃ 26. 152. 278. 404. C₄H₉ F H H H CF₃27. 153. 279. 405. C₄H₉ F F H H CF₃ 28. 154. 280. 406. C₅H₁₁ H H H H CF₃29. 155. 281. 407. C₅H₁₁ F H H H CF₃ 30. 156. 282. 408. C₅H₁₁ F F H HCF₃ 31. 157. 283. 409. C₆H₁₃ H H H H CF₃ 32. 158. 284. 410. C₆H₁₃ F H HH CF₃ 33. 159. 285. 411. C₆H₁₃ F F H H CF₃ 34. 160. 286. 412. C₇H₁₅ H HH H CF₃ 35. 161. 287. 413. C₇H₁₅ F H H H CF₃ 36. 162. 288. 414. C₇H₁₅ FF H H CF₃ 37. 163. 289. 415. C₂H₅ H H H H OCF₃ 38. 164. 290. 416. C₂H₅ FH H H OCF₃ 39. 165. 291. 417. C₂H₅ F F H H OCF₃ 40. 166. 292. 418. C₃H₇H H H H OCF₃ 41. 167. 293. 419. C₃H₇ F H H H OCF₃ 42. 168. 294. 420.C₃H₇ F F H H OCF₃ 43. 169. 295. 421. C₄H₉ H H H H OCF₃ 44. 170. 296.422. C₄H₉ F H H H OCF₃ 45. 171. 297. 423. C₄H₉ F F H H OCF₃ 46. 172.298. 424. C₅H₁₁ H H H H OCF₃ 47. 173. 299. 425. C₅H₁₁ F H H H OCF₃ 48.174. 300. 426. C₅H₁₁ F F H H OCF₃ 49. 175. 301. 427. C₆H₁₃ H H H H OCF₃50. 176. 302. 428. C₆H₁₃ F H H H OCF₃ 51. 177. 303. 429. C₆H₁₃ F F H HOCF₃ 52. 178. 304. 430. C₇H₁₅ H H H H OCF₃ 53. 179. 305. 431. C₇H₁₅ F HH H OCF₃ 54. 180. 306. 432. C₇H₁₅ F F H H OCF₃ 55. 181. 307. 433. C₂H₅ HH H H CN 56. 182. 308. 434. C₂H₅ F H H H CN 57. 183. 309. 435. C₂H₅ F FH H CN 58. 184. 310. 436. C₃H₇ H H H H CN 59. 185. 311. 437. C₃H₇ F H HH CN 60. 186. 312. 438. C₃H₇ F F H H CN 61. 187. 313. 439. C₄H₉ H H H HCN 62. 188. 314. 440. C₄H₉ F H H H CN 63. 189. 315. 441. C₄H₉ F F H H CN64. 190. 316. 442. C₅H₁₁ H H H H CN 65. 191. 317. 443. C₅H₁₁ F H H H CN66. 192. 318. 444. C₅H₁₁ F F H H CN 67. 193. 319. 445. C₆H₁₃ H H H H CN68. 194. 320. 446. C₆H₁₃ F H H H CN 69. 195. 321. 447. C₆H₁₃ F F H H CN70. 196. 322. 448. C₇H₁₅ H H H H CN 71. 197. 323. 449. C₇H₁₅ F H H H CN72. 198. 324. 450. C₇H₁₅ F F H H CN 73. 199. 325. 451. C₂H₅ H H H H NCS74. 200. 326. 452. C₂H₅ F H H H NCS 75. 201. 327. 453. C₂H₅ F F H H NCS76. 202. 328. 454. C₃H₇ H H H H NCS 77. 203. 329. 455. C₃H₇ F H H H NCS78. 204. 330. 456. C₃H₇ F F H H NCS 79. 205. 331. 457. C₄H₉ H H H H NCS80. 206. 332. 458. C₄H₉ F H H H NCS 81. 207. 333. 459. C₄H₉ F F H H NCS82. 208. 334. 460. C₅H₁₁ H H H H NCS 83. 209. 335. 461. C₅H₁₁ F H H HNCS 84. 210. 336. 462. C₅H₁₁ F F H H NCS 85. 211. 337. 463. C₆H₁₃ H H HH NCS 86. 212. 338. 464. C₆H₁₃ F H H H NCS 87. 213. 339. 465. C₆H₁₃ F FH H NCS 88. 214. 340. 466. C₇H₁₅ H H H H NCS 89. 215. 341. 467. C₇H₁₅ FH H H NCS 90. 216. 342. 468. C₇H₁₅ F F H H NCS 91. 217. 343. 469. C₂H₅ HH H H SF₅ 92. 218. 344. 470. C₂H₅ F H H H SF₅ 93. 219. 345. 471. C₂H₅ FF H H SF₅ 94. 220. 346. 472. C₃H₇ H H H H SF₅ 95. 221. 347. 473. C₃H₇ FH H H SF₅ 96. 222. 348. 474. C₃H₇ F F H H SF₅ 97. 223. 349. 475. C₄H₉ HH H H SF₅ 98. 224. 350. 476. C₄H₉ F H H H SF₅ 99. 225. 351. 477. C₄H₉ FF H H SF₅ 100. 226. 352. 478. C₅H₁₁ H H H H SF₅ 101. 227. 353. 479.C₅H₁₁ F H H H SF₅ 102. 228. 354. 480. C₅H₁₁ F F H H SF₅ 103. 229. 355.481. C₆H₁₃ H H H H SF₅ 104. 230. 356. 482. C₆H₁₃ F H H H SF₅ 105. 231.357. 483. C₆H₁₃ F F H H SF₅ 106. 232. 358. 484. C₇H₁₅ H H H H SF₅ 107.233. 359. 485. C₇H₁₅ F H H H SF₅ 108. 234. 360. 486. C₇H₁₅ F F H H SF₅109. 235. 361. 487. C₂H₅ H H H H OC₂H₅ 110. 236. 362. 488. C₂H₅ F H H HOC₂H₅ 111. 237. 363. 489. C₂H₅ F H F H OC₂H₅ 112. 238. 364. 490. C₃H₇ HH H H OC₂H₅ 113. 239. 365. 491. C₃H₇ F H H H OC₂H₅ 114. 240. 366. 492.C₃H₇ F H F H OC₂H₅ 115. 241. 367. 493. C₄H₉ H H H H OC₂H₅ 116. 242. 368.494. C₄H₉ F H H H OC₂H₅ 117. 243. 369. 495. C₄H₉ F H F H OC₂H₅ 118. 244.370. 496. C₅H₁₁ H H H H OC₂H₅ 119. 245. 371. 497. C₅H₁₁ F H H H OC₂H₅120. 246. 372. 498. C₅H₁₁ F H F H OC₂H₅ 121. 247. 373. 499. C₆H₁₃ H H HH OC₂H₅ 122. 248. 374. 500. C₆H₁₃ F H H H OC₂H₅ 123. 249. 375. 501.C₆H₁₃ F H F H OC₂H₅ 124. 250. 376. 502. C₇H₁₅ H H H H OC₂H₅ 125. 251.377. 503. C₇H₁₅ F H H H OC₂H₅ 126. 252. 378. 504. C₇H₁₅ F H F H OC₂H₅

EXAMPLE 505

The compound of the following formula

2-(difluoro[3,4,5-trifluorophenyl]oxymethyl)-7-(4-n-propylcyclohexyl)spiro-[5.3]nonane(11)

is prepared as follows:

2-(difluoro[3,4,5-trifluorophenyl]oxymethyl)-7-(4-n-propylcyclohexyl)spiro-[5.3]nonane(11) is obtained from 7-(4-n-propylcyclohexyl)spiro[5.3]nonan-2-one (9)analogously to the synthesis described in Example 1.

8.90 g (32.0 mmol) of the dithioacetal 10 are dissolved in 80 ml ofdichloromethane, and 2.8 ml (32.0 mmol) of trifluoromethanesulfonic acidare added dropwise with ice/common salt cooling. After 5 minutes, thecooling is removed, and the batch is stirred at room temperature for 45minutes. The batch is subsequently cooled to −70° C., a mixture of 7.1ml (51.0 mmol) of triethylamine and 7.10 g (48.0 mmol) oftrifluorophenol in 80 ml of dichloromethane is added, and the batch isstirred at −70° C. for 1 hour. 25.8 ml (0.160 mol) of triethylaminetris(hydrofluoride) are then added, and, after 5 minutes, 45.8 g (0.150mol) of DBH, suspended in 60 ml of dichloromethane, are added inportions over the course of about 30 minutes. After 90 minutes, thebatch is allowed to thaw and is hydrolysed using 1 M sodium hydroxidesolution and aqueous hydrogen sulfite solution. The organic phase isseparated off, washed with saturated sodium chloride solution and driedover sodium sulfate. The solvent is removed under reduced pressure, andthe residue is filtered through silica gel with n-heptane. The crudeproduct is purified by bulb-tube distillation (boiling point: 158°C./0.1 mbar), giving the spiro compound 11.

-   Δε=7.4-   Δn=0.0641

The following compounds according to the invention are obtainedanalogously to Example 505 using the corresponding precursors:

Examples R¹ L¹ L² L³ L⁴ R² 505. 631. 757. 883. C₃H₇ F F H H F 506. 632.758. 884. C₃H₇ F H H H F 507. 633. 759. 885. C₃H₇ H H H H F 508. 634.760. 886. C₂H₅ H H H H F 509. 635. 761. 887. C₂H₅ F H H H F 510. 636.762. 888. C₂H₅ F F H H F 511. 637. 763. 889. C₄H₉ H H H H F 512. 638.764. 890. C₄H₉ F H H H F 513. 639. 765. 891. C₄H₉ F F H H F 514. 640.766. 892. C₅H₁₁ H H H H F 515. 641. 767. 893. C₅H₁₁ F H H H F 516. 642.768. 894. C₅H₁₁ F F H H F 517. 643. 769. 895. C₆H₁₃ H H H H F 518. 644.770. 896. C₆H₁₃ F H H H F 519. 645. 771. 897. C₆H₁₃ F F H H F 520. 646.772. 898. C₇H₁₅ H H H H F 521. 647. 773. 899. C₇H₁₅ F H H H F 522. 648.774. 900. C₇H₁₅ F F H H F 523. 649. 775. 901. C₂H₅ H H H H CF₃ 524. 650.776. 902. C₂H₅ F H H H CF₃ 525. 651. 777. 903. C₂H₅ F F H H CF₃ 526.652. 778. 904. C₃H₇ H H H H CF₃ 527. 653. 779. 905. C₃H₇ F H H H CF₃528. 654. 780. 906. C₃H₇ F F H H CF₃ 529. 655. 781. 907. C₄H₉ H H H HCF₃ 530. 656. 782. 908. C₄H₉ F H H H CF₃ 531. 657. 783. 909. C₄H₉ F F HH CF₃ 532. 658. 784. 910. C₅H₁₁ H H H H CF₃ 533. 659. 785. 911. C₅H₁₁ FH H H CF₃ 534. 660. 786. 912. C₅H₁₁ F F H H CF₃ 535. 661. 787. 913.C₆H₁₃ H H H H CF₃ 536. 662. 788. 914. C₆H₁₃ F H H H CF₃ 537. 663. 789.915. C₆H₁₃ F F H H CF₃ 538. 664. 790. 916. C₇H₁₅ H H H H CF₃ 539. 665.791. 917. C₇H₁₅ F H H H CF₃ 540. 666. 792. 918. C₇H₁₅ F F H H CF₃ 541.667. 793. 919. C₂H₅ H H H H OCF₃ 542. 668. 794. 920. C₂H₅ F H H H OCF₃543. 669. 795. 921. C₂H₅ F F H H OCF₃ 544. 670. 796. 922. C₃H₇ H H H HOCF₃ 545. 671. 797. 923. C₃H₇ F H H H OCF₃ 546. 672. 798. 924. C₃H₇ F FH H OCF₃ 547. 673. 799. 925. C₄H₉ H H H H OCF₃ 548. 674. 800. 926. C₄H₉F H H H OCF₃ 549. 675. 801. 927. C₄H₉ F F H H OCF₃ 550. 676. 802. 928.C₅H₁₁ H H H H OCF₃ 551. 677. 803. 929. C₅H₁₁ F H H H OCF₃ 552. 678. 804.930. C₅H₁₁ F F H H OCF₃ 553. 679. 805. 931. C₆H₁₃ H H H H OCF₃ 554. 680.806. 932. C₆H₁₃ F H H H OCF₃ 555. 681. 807. 933. C₆H₁₃ F F H H OCF₃ 556.682. 808. 934. C₇H₁₅ H H H H OCF₃ 557. 683. 809. 935. C₇H₁₅ F H H H OCF₃558. 684. 810. 936. C₇H₁₅ F F H H OCF₃ 559. 685. 811. 937. C₂H₅ H H H HCN 560. 686. 812. 938. C₂H₅ F H H H CN 561. 687. 813. 939. C₂H₅ F F H HCN 562. 688. 814. 940. C₃H₇ H H H H CN 563. 689. 815. 941. C₃H₇ F H H HCN 564. 690. 816. 942. C₃H₇ F F H H CN 565. 691. 817. 943. C₄H₉ H H H HCN 566. 692. 818. 944. C₄H₉ F H H H CN 567. 693. 819. 945. C₄H₉ F F H HCN 568. 694. 820. 946. C₅H₁₁ H H H H CN 569. 695. 821. 947. C₅H₁₁ F H HH CN 570. 696. 822. 948. C₅H₁₁ F F H H CN 571. 697. 823. 949. C₆H₁₃ H HH H CN 572. 698. 824. 950. C₆H₁₃ F H H H CN 573. 699. 825. 951. C₆H₁₃ FF H H CN 574. 700. 826. 952. C₇H₁₅ H H H H CN 575. 701. 827. 953. C₇H₁₅F H H H CN 576. 702. 828. 954. C₇H₁₅ F F H H CN 577. 703. 829. 955. C₂H₅H H H H NCS 578. 704. 830. 956. C₂H₅ F H H H NCS 579. 705. 831. 957.C₂H₅ F F H H NCS 580. 706. 832. 958. C₃H₇ H H H H NCS 581. 707. 833.959. C₃H₇ F H H H NCS 582. 708. 834. 960. C₃H₇ F F H H NCS 583. 709.835. 961. C₄H₉ H H H H NCS 584. 710. 836. 962. C₄H₉ F H H H NCS 585.711. 837. 963. C₄H₉ F F H H NCS 586. 712. 838. 964. C₅H₁₁ H H H H NCS587. 713. 839. 965. C₅H₁₁ F H H H NCS 588. 714. 840. 966. C₅H₁₁ F F H HNCS 589. 715. 841. 967. C₆H₁₃ H H H H NCS 590. 716. 842. 968. C₆H₁₃ F HH H NCS 591. 717. 843. 969. C₆H₁₃ F F H H NCS 592. 718. 844. 970. C₇H₁₅H H H H NCS 593. 719. 845. 971. C₇H₁₅ F H H H NCS 594. 720. 846. 972.C₇H₁₅ F F H H NCS 595. 721. 847. 973. C₂H₅ H H H H SF₅ 596. 722. 848.974. C₂H₅ F H H H SF₅ 597. 723. 849. 975. C₂H₅ F F H H SF₅ 598. 724.850. 976. C₃H₇ H H H H SF₅ 599. 725. 851. 977. C₃H₇ F H H H SF₅ 600.726. 852. 978. C₃H₇ F F H H SF₅ 601. 727. 853. 979. C₄H₉ H H H H SF₅602. 728. 854. 980. C₄H₉ F H H H SF₅ 603. 729. 855. 981. C₄H₉ F F H HSF₅ 604. 730. 856. 982. C₅H₁₁ H H H H SF₅ 605. 731. 857. 983. C₅H₁₁ F HH H SF₅ 606. 732. 858. 984. C₅H₁₁ F F H H SF₅ 607. 733. 859. 985. C₆H₁₃H H H H SF₅ 608. 734. 860. 986. C₆H₁₃ F H H H SF₅ 609. 735. 861. 987.C₆H₁₃ F F H H SF₅ 610. 736. 862. 988. C₇H₁₅ H H H H SF₅ 611. 737. 863.989. C₇H₁₅ F H H H SF₅ 612. 738. 864. 990. C₇H₁₅ F F H H SF₅ 613. 739.865. 991. C₂H₅ H H H H OC₂H₅ 614. 740. 866. 992. C₂H₅ F H H H OC₂H₅ 615.741. 867. 993. C₂H₅ F H F H OC₂H₅ 616. 742. 868. 994. C₃H₇ H H H H OC₂H₅617. 743. 869. 995. C₃H₇ F H H H OC₂H₅ 618. 744. 870. 996. C₃H₇ F H F HOC₂H₅ 619. 745. 871. 997. C₄H₉ H H H H OC₂H₅ 620. 746. 872. 998. C₄H₉ FH H H OC₂H₅ 621. 747. 873. 999. C₄H₉ F H F H OC₂H₅ 622. 748. 874. 1000.C₅H₁₁ H H H H OC₂H₅ 623. 749. 875. 1001. C₅H₁₁ F H H H OC₂H₅ 624. 750.876. 1002. C₅H₁₁ F H F H OC₂H₅ 625. 751. 877. 1003. C₆H₁₃ H H H H OC₂H₅626. 752. 878. 1004. C₆H₁₃ F H H H OC₂H₅ 627. 753. 879. 1005. C₆H₁₃ F HF H OC₂H₅ 628. 754. 880. 1006. C₇H₁₅ H H H H OC₂H₅ 629. 755. 881. 1007.C₇H₁₅ F H H H OC₂H₅ 630. 756. 882. 1008. C₇H₁₅ F H F H OC₂H₅

EXAMPLE 1009

A liquid-crystal mixture comprising BCH-3F.F 10.80% BCH-5F.F  9.00%ECCP-3OCF₃  4.50% ECCP-5OCF₃  4.50% CBC-33F  1.80% CBC-53F  1.80%CBC-55F  1.80% PCH-5F  9.00% PCH-6F  7.20% PCH-7F  5.40% CCP-2OCF₃ 7.20% CCP-3OCF₃ 10.80% CCP-4OCF₃  6.30% CCP-5OCF₃  9.90% Compound ofExample 1 10.00%has the following properties:

Clearing point: +86.0° C.

Δε: +5.6

Δn: +0.0924

EXAMPLE 1010

A liquid-crystal mixture comprising CCH-3O1 11.23% CCH-3CF₃  6.42%CCH-5O1  8.82% CCP-2F.F.F  8.02% CCP-3F.F.F 10.42% CCP-5F.F.F  4.01%CCPC-33  2.41% CCZU-2-F  4.01% CCZU-3-F 13.62% CCZU-5-F  4.01% CH-33 2.41% CH-35  2.41% CH-43  2.41% Compound of Example 1 19.80%has the following properties:

Clearing point: +72.0° C.

Δn: +0.0605

EXAMPLE 1011

A liquid-crystal mixture comprising BCH-3F.F 10.76% BCH-5F.F  8.98%ECCP-30CF₃  4.49% ECCP-50CF₃  4.49% CBC-33F  1.80% CBC-53F  1.80%CBC-55F  1.80% PCH-6F  7.18% PCH-7F  5.39% CCP-20CF₃  7.18% CCP-30CF₃10.76% CCP-40CF₃  6.28% CCP-50CF₃  9.87% PCH-5F  8.98% Compound ofExample 505 10.24%has the following properties:

Clearing point: +73.2° C.

Δε: +5.3

Δn: +0.0885

1. Cyclobutane derivatives of the formula I

in which R¹, R² are identical or different and each, independently ofone another, denote H, halogen (F, Cl, Br or I) or a linear or branched,optionally chiral alkyl or alkoxy radical having 1 to 15 C atoms whichis unsubstituted or mono- or polysubstituted by halogen and in which oneor more CH₂ groups may each be replaced, independently of one another,by —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CH═CH—, —CH═CF—, —CF═CF—,—C≡C— or

 in such a way that heteroatoms are not linked directly to one another,—CN, —SCN, —NCS, —SF₅, —SCF₃, —CF₃, —CF═CF₂, —CF₂CF₂CF₃, —OCF₃, —OCHF₂,—CF₂CH₂CF₃ or —OCH₂CF₂CHFCF₃, A is identical or different and in eachcase, independently of one another, denotes a) trans-1,4-cyclohexylene,in which, in addition, one or more non-adjacent CH₂ groups may bereplaced by —O— and/or —S— and in which, in addition, one or more Hatoms may be replaced by F, b) 1,4-phenylene, in which one or two CHgroups may be replaced by N and in which, in addition, one or more Hatoms may be replaced by halogen (F, Cl, Br or I), —CN, —CH₃, —CHF₂,—CH₂F, —OCH₃, —OCHF₂ or —OCF₃, c) a radical from the groupbicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl,spiro[3.3]heptane-2,6-diyl, naphthalene-2,6-diyl,decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyland piperidine-1,4-diyl, or d) 1,4-cyclohexenylene, Z is identical ordifferent and in each case, independently of one another, denotes —O—,—CH₂O—, —OCH₂—, —CO—O—, —O—CO—, —CF₂O—, —OCF₂—, —CF₂CF₂—, —CH₂CF₂—,—CF₂CH₂—, —CH₂CH₂—, —CH═CH—, —CH═CF—, —CF═CH—, —CF═CF—, —CF═CF—COO—,—O—CO—CF═CF—, —C≡C— or a single bond, m, n are identical or differentand, independently of one another, denote 0, 1 or 2, and o denotes 0or
 1. 2. Compounds according to claim 1, characterised in that both odenote
 0. 3. Compounds according to claim 1, characterised in that botho denote
 1. 4. Compounds according to claim 2, characterised in thatthey have one of the following formulae:

in which L¹, L², L³, L⁴, L⁵ and L⁶, are identical or different and,independently of one another, denote H or F.
 5. Compounds according toclaim 3, characterised in that they have one of the following formulae:

in which L¹, L², L³, L⁴, L⁵ and L⁶, are identical or different and,independently of one another, denote H or F.
 6. Compounds according toat least claim 1, characterised in that R¹ denotes H or a linear alkylradical having 1 to 10 C atoms.
 7. Compounds according to claim 1,characterised in that R² denotes H, a linear alkoxy radical having 1 to10 C atoms, —F, —Cl, —CF₃, —OCF₃, —OCHF₂, —CN, —NCS or —SF₅.
 8. Use ofcompounds of the formula I according to claim 1 as component(s) ofliquid-crystalline media.
 9. Liquid-crystalline medium having at leasttwo liquid-crystalline components, characterised in that it comprises atleast one compound of the formula I according to claim
 1. 10.Liquid-crystal display element, characterised in that it contains, asdielectric, a liquid-crystalline medium according to claim
 9. 11.Reflective or transflective liquid-crystal display element,characterised in that it contains, as dielectric, a liquid-crystallinemedium according to claim
 9. 12. Electro-optical display element,characterised in that it contains, as dielectric, a liquid-crystallinemedium according to claim 9.